Ecological risk assessment problem formulation

A number of EIA theorists believe in incorporating formal RA methods into EIA as a way to cope with uncertainties, especially in impact prediction where a formal framework for ecological risk assessment (EcoRA) is already developed. It includes three generic phases problem formulation, analysis, and risk characterization followed by risk management. The analysis phase includes an exposure assessment and an ecological effects assessment (see, e.g., US EPA (1998)). 

Problem Formulation for Probabilistic Ecological Risk Assessments... 

The overall ecological risk assessment process is shown in Figure 28.1 and includes three primary phases (1) problem formulation, (2) analysis, and (3) risk characterization. Problem formulation includes the development of a conceptual model... 

The ecological risk assessment was conducted in accordance with the USEPA guidance document Guidelines for Ecological Risk Assessment (USEPA, 1998) . A four-step assessment process was adopted problem formulation, exposure characterization, characterization of ecological effects and risk evaluation. 

Ecological risk assessment of chemical mixtures thus has to deal with a variety of field phenomena, a possible range of assessment endpoints, and a variety of assessment approaches. Moreover, there exists a huge variety in the regulatory questions and problem formulations addressed in ecological risk assessment of chemical mixtures. Examples include the protection of specific species against well-defined mixtures (like PCBs and PAHs), the protection of an undefined concept like the ecosystem, and retrospective assessments for highly or diffusely contaminated systems. 

A. Hart, S. Person, J. Shaw, Problem Formulation for Probabilistic Ecological Risk Assessments , Quantifying Uncertainty in Risk Assessment Practical Approaches and their Application to Estimating Ecological Risks of Pesticides , report on the findings of a workshop held in Pensacola, FL, USA., SETAC, February 24 to March 1,2002 (in preparation). 

Perhaps a more useful means of quantifying structural data is to use a similarity measurement. These are reviewed by Ludwig and Reynolds (1988) and form the basis of multivariate clustering and ordination. Similarity measures can compare the presence of species in two sites or compare a site to a predetermined set of species derived from historical data or as an artificial set comprised of measurement endpoints from the problem formulation of an ecological risk assessment. The simplest similarity measures are binary in nature, but others can accommodate the number of individuals in each set. Related to similarity measurements are distance metrics. Distance measurements, such as Euclidean distance, have the drawbacks of being sensitive to outliers, scale, transformations, and magnitudes. Distance measures form the basis of many classification and clustering techniques. 

As mentioned before, the ecological risk assessment is characterized by a problem formulation process, analysis containing characterizations of exposure and effects, and a risk characterization process. Several outlying boxes serve to emphasize the importance of discussions during the problem formulation process between the risk assessor and the risk manager, and the critical nature of the acquisition of new data, verification of the risk assessment, and monitoring. The next few sections detail each aspect of this framework. 

The first phase of the framework is problem formulation. Problem formulation includes a preliminary characterization of exposure and effects, as well as examination of scientific data and data needs, policy and regulatory issues, and site-specific factors to define the feasibility, scope, and objectives for the ecological risk assessment. The level of detail and the information that will be needed to complete the assessment also are determined. This systematic planning phase is proposed because ecological risk assessments often address the... 

The interaction between data acquisition and ecological risk assessment is also shown in Figure 1. In this report, a distinction is made between data acquisition (which is outside of the risk assessment process) and data analysis (which is an integral part of an ecological risk assessment). In the problem formulation and analysis phases, the risk assessor may identify the need for additional data to complete an analysis. At this point, the risk assessment stops until the necessary data are acquired. When a need for additional data... 

The next three sections of this report are arranged to follow the framework sequentially Section 2 describes problem formulation this section is particularly important for assessors to consider when specific assessment endpoints are not determined a priori by statute or other authority. Section 3 and Section 4 discuss analysis and risk characterization, respectively. Section 5 defines the terms used in this report, and Section 6 provides literature references. The lists of ecological risk assessment issues at the end of Section 1 to Section 4 highlight areas for further discussion and research. EPA believes that these... 

Problem formulation is the first phase of ecological risk assessment and establishes the goals, breadth, and focus of the assessment. It is a systematic planning step that identifies the major factors to be considered in a particular assessment, and it is linked to the regulatory and policy context of the assessment. 

EPA risk assessment framework and establish a common approach with its paradigm. The U.S. EPA s overall ecological risk assessment process is illustrated in Fig. 1. It consists of three basic elements Problem Formulation, Analysis, and Risk Characterization. 

The problem-formulation step of an ecological risk assessment concludes with the development of an analysis plan. The analysis plan identifies which assessment endpoints and risk hypotheses articulated by the conceptual diagram will be pursued in the next phase of the risk assessment analysis (Figure 9.1). The decision as to which assessment endpoints to include in the risk assessment is guided by professional judgments on such questions such as the importance of a stressor-receptor relationship, its relationship to ecosystem structure, and the quality and availability of data to analyze it. 

Like a human health risk assessment, an ecological risk assessment turns on analyses of exposure and effect. Exposure analyses are based on measures of exposure, and effects analyses are based on measures of effect both types of measures are tentatively identified in the problem-formulation phase. There can be substantial interaction between exposure and effects analyses in natural systems, because a stressor may trigger a cascade of effects, some of which result in additional stressors and effects. For example, the effect of a logging road as a primary stressor is to create secondary stressors such as increased siltation of streams, and the primary effect of... 

In formal EcoRA framework three phases of risk analysis are identified problem formulation, analysis, and risk characterization followed by risk management. The analysis phase includes an exposure assessment and an ecological effects assessment (see Figure 2). 

This initial and perhaps most important part of the assessment defines the nature and scope of the ERA, describes the sources of potential risk ( stressors ), identifies the ecological resources at risk ( end-points ), considers the nature of the ecological impacts in relation to the stressors, and produces a conceptual model of the overall assessment. Thus, problem formulation essentially encapsulates the entire ERA process. Execution of this step requires collaboration among risk managers and risk assessors to define the assessment objectives and develop the corresponding conceptual model. This model, like most, should be viewed as dynamic and subject to change throughout the ERA in relation to modifications to the objectives and the development of new data and information. 

Many factors can influence the utility of available ecological effects data for problem formulation. For example, the applicability of laboratory-based tests may be affected by any extrapolations required to specific field situations, while the interpretation of field observations may be influenced by factors such as natural variability or the possible presence of stressors other than the ones that are the primary focus of the risk assessment... 

Data are evaluated by considering their relevance to the measurement and assessment endpoints selected during problem formulation. The analysis techniques that will be used also are considered data that minimize the need for extrapolation are desirable. Data quality (e.g., sufficiency of replications, adherence to good laboratory practices) is another important consideration. Finally, characteristics of the ecosystem potentially at risk will influence what data will be used. Ideally, the test system reflects the physical attributes of the ecosystem and will include the ecological components and life stages examined in the risk assessment. 

Problem formulation. Within this process all available information about a contaminated site is collected including the nature of the contaminants and their sources, obvious effects and potential receptors as well as environmental recipients. Within this very first stage of the risk assessment procedure, an assessment endpoint has to be determined. Assessment endpoints are the expression of an environmental value (represented by an ecological entity) that is at risk, e.g. a distinct population that faces harm due to pollution. It has to be emphasised that toxicity-test endpoints or other measurement endpoints (in general, measured effects under test conditions) in most cases do not represent assessment endpoints (response of population or ecosystem in the field). Measurement endpoints should be representative for assessment endpoints or have a known relationship to the assessment endpoint allowing the extrapolation of data. 

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